Carbonatites in plate-collision zones: implications for mantle processes, carbon cycling and rare-earth metallogeny

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Carbonatites are a remarkable manifestation of low-volume, mantle-derived magmatism in terms of their composition, physical properties and industrial potential. These rocks and their weathering products have long served as the principal source of such technologically “critical” metals as rare-earth elements (REE) and niobium. Despite the large volume of literature published on this subject, no consensus has been reached yet on such key issues as the role of crust recycling and magma-crust interaction in carbonatite petrogenesis, the nature of processes responsible for the concentration and dispersal of rare metals in carbonatites subjected to fluid infiltration, deformation and metasomatism, and the applicability of specific geochemical characteristics (e.g., element or isotope ratios) to exploration vectoring. In recent years, revision of the previously existing models of carbonatite evolution has been necessitated due to: an increasing number of carbonatite discoveries in (paleo)orogenic belts, the realization that some of the most important REE deposits are associated with plate-collision processes, and new isotopic evidence. The proposed research program is aimed at acquiring new data to address the existing knowledge gaps and to provide a basis for the development of a petrogenetic-metallogenic model for carbonatitic magmatism in plate-collision zones. The novelty of the proposed work is in its integrated and inclusive approach, and its focus on rocks and mineral deposits for which little isotope data are presently available. The program builds on my 25 years of research experience with carbonatites and ongoing collaboration with the Manitoba Geological Survey. The principal expected outcomes of the next Discovery Grant cycle are an improved understanding of the mantle source(s) of carbonatites in plate-collision zones, of geodynamic and structural controls on carbonatitic magmatism in these settings, and of the relative contribution of source-specific, magmatic and postemplacement processes to the development of rare-metal deposits. Progress in these areas will provide a basis for refining the current mineral exploration practices. Other benefits of the proposed program will be in the publication of new geological data for a number of potential exploration targets, and in the training of highly-qualified personnel equipped with theoretical knowledge and practical skills required for mineral exploration and research. The University of Manitoba has unique instrumental capabilities for providing this type of training. My previous work on carbonatites has been recognized in, and supported by, academic, industrial and government sectors. The results of the proposed research will be disseminated through publications, presentations at conferences and mining conventions, workshops for knowledge users and other forms of outreach.